• Research in Plant Disease
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• v.9 no.3
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• pp.137-144
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• 2003

This study was conducted to clarify developmental characteristics of scab in potato fields in Jeju island, Korea from 1995 to 1999. Occurrence of potato scab increased with repeated cultivaton of potato and high soil pH in the fields. Incidence of the disease was high as 54.8％ in the repeatedly cultivated potato fields but relatively low as 20.8~26.3% in the non-cultivated fields and in the fields where barley and Chinese cabbage were formerly cultivated. A total of 66 isolates were obtained from the diseased patato tubers and identified as Streptomyces scabies, S.turgidiscabies and S. acidiscabies. The isolation frequency of each Streptomyces species was 37.7%, 14.8% and 18.0%, respectively. The optimum temperature for mycelial growth of the Streptomyces spp. was $28~30^{\circ}C$, and the optimum pH for that 6~7.

• Research in Plant Disease
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• v.10 no.2
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• pp.138-141
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• 2004

It was conducted to find out the effect of chemical treatment on seed tubers and soil to control potato common scab in Jeju Island in 2001. Although the treatment of soil disinfection with Dazomet Gr. (30kg/10a) was more effective comparing to the treatment of seed disinfection and the untreated, the control value was merely 40.5%. However, the combined treatment of soil and seed disinfection was considerably more effective to reduce the percentage of infection and infection area, and increase the production of marketable tubers and also increase the control value. Therefore, the combined treatments are demanded to reduce the scab incidence in Jeju field conditions.

• Korean Journal of Organic Agriculture
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• v.20 no.4
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• pp.687-702
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• 2012

The objective of this study was to determine crop rotation effects on potato yield, soil chemical and microbiological properties from a short-term field experiment from 2010 to 2011 in Jeju Island, Korea. Potato cropping systems included continuous and rotation sequences of soybean (Glycine max(L.) Merr.), barley (Hordeum vulgare var. hexastichon), rapeseed (Brassica napus L.) and broccoli (Brassica oleracea var. italica). Crop rotations increased the yields of potato from 31% to 52% compared with continuous potato. Marketable yield of potato was highest under soybean plus rapeseed rotation by $20.97MT\;ha^{-1}$ and lowest under continuous cropping by $11.95MT\;ha^{-1}$. The incidence and severity of scab disease was significantly lower in tubers from crop rotation with soybean plus barley. Differences in marketable tuber yields among rotations were associated with potato scab disease. Especially, incidence and severity of potato scab were strongly correlated with soil pH, exchangeable calcium, and bacteria population of the soil. Crop rotations significantly increased soil pH, available phosphate, exchangeable K and Ca, especially in crop rotations with soybean plus barley or rapeseed. Soil microbial biomass C of crop rotations with soybean plus barley or rapeseed, was also significantly higher compared with monoculture. In conclusion, crop rotation may decrease the incidence of soil-born pathogen by increasing soil chemical properties and soil microbial biomass. Overall, potato crop productivity was generally maintained in rotations that contained soybean plus barley or rapeseed but declined under continuous cropping system.

• Korean Journal of Breeding Science
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• v.42 no.3
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• pp.207-211
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• 2010

'Taedong Valley' is a high yielding and processing potato cultivar, which is a clonal selection resulting from a cross between 'W870' and 'A88431-1'. It is a medium maturating cultivar with medium plant height and light green foliage. 'Taedong Valley' has profuse flowering habit and light purple flowers. Tubers are smooth, round, and with yellow skin, light yellow flesh, medium eye depth. Tubers have medium dormancy and good keeping quality. 'Taedong Valley' has stable yield under wide range of climatic conditions. It is resistant to common scab and potato virus Y, but moderately susceptible to late blight. It is also resistant to most of the disorders, particularly dehiscence, hollow heart and internal brown spots. This cultivar has high level of tuber uniformity and capable of yielding 43.6 t/ha which is about 9.0% higher than the control potato cultivar 'Atlantic' under optimum agronomical practices.

• Korean Journal of Organic Agriculture
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• v.8 no.3
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• pp.99-109
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• 2000

This experiment was conducted to investigate the changes of rate of infected common scab and yield characteristics of fall potato(Solanum tuberosum L.) where green manual crops had been previously cultivated, crushed and tilled and P\ulcornerE transparent vinyl film had been mulched and tunneled to solar heating of soil from May 21. 1998 to July 28. 1998. The total yields of green manual crops which had been previousely cultivated were as followed order : pioneer 855F(64.3MT/ha), soybean(25.0MT/ha), red clover and orchardgrass. The average below-ground temperature at the depths of 5, 10 and 20cm were 54, 45 and 44$^{\circ}C$ during the mulching period, respectively The rate of infected area per potato tuber of common scab decreased by solar heating the soils with mulching after the soybean and red clover cultivation as with previous croppings. Plant height, SPAD(soil plant analysis development) reading, fresh weight of stems, and fall potato's tuber yields tended to increase by the cultivation of green manual crops and mulching of P\ulcornerE film. Fall potato's tuber yields were remarkably affected in the plot of soybean, red clover and pioneer 855F+cultivation of fall potato. T-N, K and Ca contents of fall potato(stem and tuber) also tended to increase by the cultivation of green manual crops and mulching of P\ulcornerE film. T-N, K and Ca contents of soil tended to increase after the cultivation of green manual crops and mulching of P\ulcornerE film and then reduced to contents of soil before green manual planting after potato harvesting.

• Proceedings of the Korean Society of Plant Pathology Conference
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• 2003.10a
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• pp.134.2-135
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• 2003

The plant-pathogenic species S. scabies, S. acidiscabies, and S. turgidiscabies cause the scab disease of potato and produce the phytotoxins, thaxtomins. necl, a gene conferring a necrogenic phenotype, is involved in pathogenicity and physically linked to the thaxtomin A biosynthetic genes. Identification of the pathogenic strains of Streptomyces from soil was performed through the polymerase chain reaction by using specific pathogenicity primer sets derived from the necl gene sequences of Streptomyces smbies. The DNA was extracted from soil using a bead-beating machine and modifications of the FastPrep system. The DNA was suitable for direct use in the PCR. The PCR products showed the bands of approximately 460 bp. This methods can be very usuful in identifying species responsible for scab diseases and studying on the ecology of plant-pathogenic Streptomyces spp.

• Applied Biological Chemistry
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• v.47 no.2
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• pp.164-169
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• 2004

In the course of our screening for biocontrol agent (BCA) against Streptomyces scabiei and S. turgidiscabies causing potato scab using 5,000 actinomtcete isolates, 9 antagonistic strains were selected as BCA candidates through in vitro and in vivo assay. An antagonistic strain, A020645 was highly resistant to some pesticides and antibiotics such as dazomet and mancozeb and showed high control value in vivo. Two bioactive compounds (compound A, B) were purified by anion exchange chromatography, solid phase (ODS) extraction, TLC and reverse phase HPLC. Their chemical structures are now thought to be nucleoside derivative as determined by $^1H-NMR$ data analysis. Their full chemical structures would be elucidated through $^{13}C-NMR$, HMQC and HMBC analyses. Further studies will be focused on fitness in soil and formulation of the BCA candidates.

• Journal of Environmental Science International
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• v.32 no.11
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• pp.777-788
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• 2023

Potato common scab disease is caused by pathogens belonging to Streptomyces spp. and results in a serious yield loss worldwide. Despite decades of research aimed at disease management, a definitive control method remains undiscovered. This study aims to explore the correlation between the C/N ratio and urea application with potato common scab pathogen dynamics and disease severity. We applied sawdust with a high C/N ratio and urea into the soil prior to potato cropping, both in pot and field experiments. Disease severity assessments and quantification of the TxtB gene were conducted at the harvest stage. Furthermore, culture experiments were performed to assess the direct impact of urea on the pathogen. Our findings revealed that higher disease severity was correlated with a high C/N ratio application and pathogenic gene quantity. Urea exhibited a direct influence on S. scabiei activity, reducing the disease severity in pot experiments. However, the effects of urea application on disease suppression in the conductive field were inconclusive. Although the results of urea application experiments displayed inconsistencies between pot and field trials, urea worked as the control to suppress S. scabiei activity. Further investigations are needed under various field conditions to confirm these findings.

• Research in Plant Disease
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• v.26 no.1
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• pp.57-60
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• 2020

Citrus scab symptoms were observed on leaves of trifoliate orange (Poncirus trifoliata) in open field of Citrus Research Institute, National Institute of Horticultural and Herbal Science. Typical scab pustules were formed and they were elevated protuberances form and light brown to grey. The pathogens were isolated from the symptomatic leaves and then were identified to Elsinoë fawcettii by morphological characteristics, pathogenicity and PCR assay. The morphological characteristics of colonies formed very slow-growing, pulvinate, or raised and deeply fissured, gummy to mucoid or tomentose colonies on potato dextrose agar medium. The pathogens were pathogenic to leaves of Satsuma mandarin, lemon, sour orange and grapefruit with typical scab symptoms. In PCR assay, specific amplified of products of 717 bp with Efaw-1 and 384 bp with Efaw-2 were observed from trifoliate isolates and E. fawcettii as reference but not from E. australis. This is first report of trifoliate orange being positive for citrus scab disease.

• The Plant Pathology Journal
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• v.19 no.1
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• pp.13-18
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• 2003

From 1996 to 1999, potato-growing areas in Korea were surveyed for identification and distribution of potato scab pathogens. Potato scab was widely distributed in the mass cultivation areas, especially in Jriu island, southern areas of Chonnam and Gyounggi provinces, and the alpine area of Gangwon province. Jeju island was the most affected area by this disease. A total of 55 Streptomyces strains were isolated from potato scab lesions, among which 40 strains were pathogenic on progeny tubers. Among the pathogenic strain, 21 strains were identified as previously described S. scabies, 7 Strains as S. turgidiscabies, and 5 Strains as S. acidiscabies, while 7 strains were observed as having distinct phenotypic properties. These strains were classified into six distinct clusters based on phenotypic characteristics and selected representative strains for each cluster. S. scabies (S33) had grey spores in a spiral chain. Mean-while, S. turgidiscabies (S27) had grey spores, S. acidiscabies (S71) had white spores, S. luridiscabiei (S63) had yellow-white spores, S. puniciscabiei (S77) had purple-red spores, and S. niveiscabiei (S78) had thin and compact white spores, all in a rectiflexuous chain. Pathogenicity was determined by the production of thaxtomin A and homologs of necl and ORFtnp genes. In TLC, representative strains S27, S71, S63, S77, and S78 produced a yellow band that co-migrated with the authentic thaxtomin A. However, thaxtomin A was not detected in chloroform extracts from oatmeal broth culture and Slice tuber tissue of S. luridiscabiei (S63) and S. puniciscabiei (S77) by HPLC analysis. In addition, no homologs of necl and ORFtnp genes in S. acidiscabies (S71), S. luridiscabiei (S63), S. puniciscabiei (S77), and S. niveiscabiei (S78) were detected by PCR and Southern hybridization analysis.